We are broadly interested how animals affect the movement of energy and nutrients in an ecosystem. Accordingly, we focus on diet and nutrition because those determine which resources are used by the animal, and how the animal fits into the food web. Under this broad umbrella we ask diverse questions. Some are fundamental/basic science questions, others are applied to specific problems such as the effects of species invasion, urban development, and climate change. Our work is based on field studies in aquatic ecosystems (streams, lakes, estuaries, or coastal systems). Our field sites are located in Canada, USA, Brazil, Trinidad and Tobago.
Here are some of our current projects:
What is the effect of urban development on food webs and ecosystem processes?
Urbanization is the most urgent threat facing aquatic ecosystems today. Characterizing the effects of urbanization on aquatic ecosystems is difficult because urbanization affects a myriad of interacting factors that are difficult to tease apart. Vancouver Island, British Columbia, is an ideal place to study the impacts of urbanization on aquatic ecosystems because we are within driving distance to numerous watersheds with various degrees and kinds of urban land use change. We currently have a few on going projects on the island, in both freshwater and marine environments. We are also collaborating with Drs. Rosana Mazzoni, Eugenia Zandonà and Piatã Marques to study the effects of urbanization on stream ecosystems and food webs in Brazil.
How does phenotypic evolution affect ecosystem processes and food webs? Ecosystems respond to human-induced disturbances in multiple, interacting ways. Individuals can grow and reproduce faster or more slowly, populations can expand or shrink, communities can become richer or poorer, and environmental conditions change. All of this can affect the movement of energy and nutrients within and among ecosystems. Characterizing how responses at the level of the individual, population, and community interact with each other is key for understanding how disturbances affect ecosystem process. We are interested in characterizing the role of phenotypic evolution, defined as heritable change in the distribution of organismal characteristics (traits) across generations. We ask whether phenotypic evolution can generate meaningful changes in ecosystem processes and food webs, especially when other aspects (e.g. population size, community composition) also vary. Ultimately our goal is to understand the role of phenotypic evolution in human-induced disturbances such as climate change, species introductions or losses, or land use change. We use three evolutionary models: guppies (Poecilia reticulata), killifish (Rivulus hartii), and threespine stickleback (Gasterosteus aculeatus) to study how changes in fish traits affect nutrient recycling, photosynthesis, community respiration, leaf decomposition, and food web structure.
What factors control nutrient recycling in freshwater ecosystems? Animals play an important role in the movement and transportation of chemical elements either within or between ecosystems. Fish and invertebrates consume elements with their diets, some of these elements are used to build new tissues, others are excreted or egested. Nutrient recycling, the process by which animals recycle essential inorganic elements in their waste, is important for the ecosystem. The dissolved wastes of fish and invertebrates contain inorganic forms of nitrogen and phosphorus which are required by primary producers, and which can limit primary and microbial production in aquatic ecosystems. One of our research goals is to understand the environmental and organismal factors that control nutrient recycling. We are especially interested in how it is affected by human-induced disturbances.